(1) Field of the Invention
The present invention relates to a sliding member including a sliding layer and a steel back metal, which has high corrosion resistance and high bonding strength between the sliding layer and the steel back metal.
(2) Description of Related Art
Sintered copper alloy materials having a porosity of approximately 5-25% have been conventionally used for a sliding member of a fuel injection pump. A liquid fuel is supplied from an outer surface side of a cylindrical sliding member to an inner surface (sliding surface) side thereof through pores existing in the sliding member, and the sliding member is provided with a lubricating fluid film of the liquid fuel on the inner surface (sliding surface) to support a high-speed rotating shaft. Such sintered copper alloy materials have a problem that the copper alloy is subjected to corrosion due to organic acids or sulfur contained in the fuel, and then the copper corrosion products contaminate the fuel. For this reason, sintered copper alloy sliding materials including Ni, Al and Zn have been proposed to improve the corrosion resistance (see e.g. JP-A-2002-180162, JP-A-2013-217493 or JP-A-2013-237898).
On the other hand, sliding members made of multi-layered sliding materials have been conventionally used. The multi-layered sliding materials include a porous sintered layer of a copper alloy provided on a surface of a steel back metal through a copper plating layer, and further pores and a surface of the porous sintered layer are impregnated and covered with a resin composition (see, e.g. JP-A-2002-61653 and JP-A-2001-355634). It has been proposed to apply such multi-layered sliding materials to the sliding member of the fuel injection pump (see e.g. JP-A-2013-83304).